Thomas Marius Joseph Butler MBE (21 July 1912 – 20 April 1970) was a Detective Chief Superintendent in the Metropolitan Police in London. He was most notable for leading the team of detectives that investigated the Great Train Robbery in 1963. He never married and lived with his mother. Butler was arguably the most renowned head of the Flying Squad in its history. He became known as "One Day" Tommy for the speed with which he apprehended criminals and the "Grey Fox" for his shrewdness.